Semiconductor light emitting device

ABSTRACT

A semiconductor light emitting device includes: a first conductive semiconductor layer including first and second areas; an active layer disposed on the second area; a second conductive semiconductor layer disposed on the active layer; first and second electrode branches disposed on the first and second conductive semiconductor layers, respectively; a first electrode pad electrically connected to the first electrode branch and disposed on the first electrode branch; and a second electrode pad electrically connected to the second electrode branch and disposed on the second electrode branch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. Application No. 13/223,877,filed on Sep. 1, 2011, which claims the priority of Korean PatentApplication No. 10-2010-0107809 filed on Nov. 01, 2010, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light emitting device.

2. Description of the Related Art

A light emitting diode, a type of semiconductor light emitting device,is a semiconductor device capable of generating light of various colorsaccording to electron hole recombination in p and n type semiconductorjunction parts when current is applied thereto. Compared with a lightemitting device based on a filament, the semiconductor light emittingdevice has various advantages such as a long life span, low powerconsumption, excellent initial driving characteristics, high vibrationresistance, and the like, so demand for the semiconductor light emittingdevice continues to grow. In particular, recently, a group III-nitridesemiconductor capable of emitting short-wavelength blue light has cometo prominence.

In the nitride semiconductor light emitting device, electrodes aregenerally arranged in a horizontal direction, narrowing a current flow.The narrow current flow increases an operation voltage Vf of the lightemitting device, degrading current efficiency, and in addition, thelight emitting device may become vulnerable to an electrostaticdischarge. Thus, in an effort to uniformly spread current on the overalllight emission surface, the electrodes are divided into pads and fingersand disposed thusly.

However, in such a structure, an active layer is etched to expose afirst conductive semiconductor layer, and a first pad and finger areformed on the first conductive semiconductor layer and a second pad andfinger are formed on a second conductive semiconductor layer. Thus, thearea of the active layer is reduced and a uniform space between theelectrodes cannot be secured to cause non-uniform current spreading.

Thus, the object of the present invention is to obtain uniform currentspreading by maintaining a uniform interval between the electrodes of asemiconductor light emitting device, and improve the luminance of thesemiconductor light emitting device by avoiding a loss of (i.e.,reduction in) an active layer resulting from etching.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a semiconductor lightemitting device having electrodes for minimizing a loss of light andimproving a current spreading effect.

According to an aspect of the present invention, there is provided asemiconductor light emitting device including: a first conductivesemiconductor layer including first and second areas; an active layerdisposed on the second area; a second conductive semiconductor layerdisposed on the active layer; first and second electrode branchesdisposed on the first and second conductive semiconductor layers,respectively; a first electrode pad electrically connected to the firstelectrode branch and disposed on the first electrode branch; and asecond electrode pad electrically connected to the second electrodebranch and disposed on the second electrode branch.

The first and second areas may have a stripe shape.

The first and second electrode branches may have a stripe shape.

A plurality of first and second electrode branches may be disposed andalternately formed.

The semiconductor light emitting device may further include: aninsulating part formed on the first and second conductive semiconductorlayers.

The insulating part may allow at least a portion of each of uppersurfaces of the first and second electrode branches to be exposed.

The first and second electrode pads may be disposed on the exposedportions of the upper surfaces of the first and second electrodebranches, respectively.

The insulating part may cover the upper portions of the first and secondelectrode branches, and at least one first conductive via electricallyconnected to the first electrode branch and at least one secondconductive via electrically connected to the second electrode branch maybe penetratingly formed through portions of the insulating part in athicknesswise direction.

The first and second conductive vias may be penetratingly formed throughthe insulating part in a vertical direction.

The first and second electrode pads may be disposed on the insulatingpart, and the first electrode pad may be electrically connected to thefirst electrode branch through the first conductive via, and the secondelectrode pad may be electrically connected to the second electrodebranch through the second conductive via.

The semiconductor light emitting device may further include: a firstconnection part extending from the first electrode pad to the firstconductive via along the upper surface of the insulating part, and asecond connection part extending from the second electrode pad to thesecond conductive via along the upper surface of the insulating part.

At least one of the first and second connection parts may be provided asa plurality of connection parts.

The first connection part may be connected to the plurality of firstconductive vias, and the second connection part may be connected to theplurality of second conductive vias.

The upper surface of the insulating part may have a rectangular shape,and the first conductive vias may be arranged along one side of theupper surface of the insulating part and the second conductive vias maybe arranged along the other side opposed to the one side.

The upper surface of the insulating part may have a rectangular shape,and the second electrode pads may be disposed to be adjacent to onecorner and neighboring another corner of the upper surface of theinsulating part, and the first electrode pad may be disposed at aposition spaced apart by the same distance from the respective secondelectrode pads.

The insulating part may be formed to include a silicon oxide.

The semiconductor light emitting device may further include: atransparent electrode layer formed on the upper surface of the secondconductive semiconductor layer.

The second electrode branch may be disposed on an upper surface of thetransparent electrode layer.

At least one of the first and second electrode pads may be disposed as aplurality of electrode pads.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1 a and 1 b are a schematic sectional view and a plan view of asemiconductor light emitting device according to an exemplary embodimentof the present invention;

FIGS. 2 a and 2 b are a schematic sectional view and a plan view of asemiconductor light emitting device according to an exemplary embodimentof the present invention;

FIG. 3 is a schematic sectional view of a semiconductor light emittingdevice according to another exemplary embodiment of the presentinvention; and

FIGS. 4 a to 4 e are a schematic perspective view, a plan view, and asectional view showing a semiconductor light emitting device accordingto another exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

The invention may, however, be embodied in many different forms andshould not be construed as being limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. In the drawings, the shapes anddimensions may be exaggerated for clarity, and the same referencenumerals will be used throughout to designate the same or likecomponents.

FIGS. 1 a and 1 b are a schematic sectional view and a plan view of asemiconductor light emitting device according to an exemplary embodimentof the present invention. Specifically, FIG. 1 a is a sectional viewtaken along line X-X′ in FIG. 1 b.

With reference to FIGS. 1 a and 1 b, a semiconductor light emittingdevice according to the present exemplary embodiment includes a firstconductive semiconductor layer 110 including first and second areas, anactive layer 120 disposed on the second area, a second conductivesemiconductor layer 130 disposed on the active layer 120, first andsecond electrode branches 111 and 131 respectively disposed on the firstand second conductive semiconductor layers 110 and 130, a firstelectrode pad 112 electrically connected to the first electrode branch111 and disposed to be separated from the first conductive semiconductorlayer 110, a second electrode pad 132 electrically connected to thesecond electrode branch 131 and disposed to be separated from the secondconductive semiconductor layer 130, and an insulating part 140 formed onthe first and second conductive semiconductor layers 110 and 130.Hereinafter, the respective elements and their connective relationshipswithin the semiconductor light emitting device according to the presentexemplary embodiment will be described in detail with reference to theaccompanying drawings.

In the light emission structure including the first and secondconductive semiconductor layers 110 and 130 and the active layer 120formed between the first and second conductive semiconductor layers, thefirst area may be defined as an area of the first conductivesemiconductor layer 110 exposed by removing a portion of the lightemission structure, and the second area may be defined as the otherremaining area, excluding the first area. This configuration can beobtained through a process of selectively etching a portion of the lightemission structure as could be easily understood by a person skilled inthe art to which the present invention pertains.

Also, in the light emission structure, the first and second conductivesemiconductor layers 110 and 130 may be made of a nitride semiconductor,specifically, a material expressed by an empirical formulaAl_(x)In_(y)Ga_((1-x-y))N (Here, 0≦x≦1, 0≦y≦1, 0≦x+y≦1). For example,the material may include GaN, AlGaN, and InGaN. The active layer 120formed between the first and second conductive semiconductor layers 110and 130 emits light having certain energy according to electron holerecombination and may have a multi-quantum well (MQW) structure in whicha quantum well and a quantum barrier are alternately stacked. In thiscase, for example, an InGaN/GaN structure may be used as the MQWstructure. Meanwhile, the first and second conductive semiconductorlayers 110 and 130 and the active layer 120 may be formed by using asemiconductor layer growing process such as metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phaseepitaxy (HVPE), or the like, well known in the art.

Preferably, the first and second areas are formed to be parallel in alengthwise direction. With such a configuration, the formation of astructure for maximizing a current spreading effect can be facilitatedin disposing electrode branches and electrode pads. However, the presentinvention is not limited thereto, and various other forms of exposingareas can be employed so long as they can expose the first and secondconductive semiconductor layers 110 and 130 and connect them toelectrode branches.

The first and second electrode branches 111 and 131 are disposed on thefirst and second conductive semiconductor layers, respectively, exposedas described above. Preferably, the first and second electrode branches111 and 131 may be formed to be in direct contact with the first andsecond conductive semiconductor layers 110 and 130, respectively.Accordingly, the first and second electrode branches 111 and 131 can befirmly electrically connected to the upper surfaces of the first andsecond conductive semiconductor layers 110 and 130. More preferably, thefirst and second areas are formed to be parallel to each other in alengthwise direction and the first and second electrode branches 111 and131 may be formed in a linear manner in the same direction. Also, in thepresent exemplary embodiment, in order to make a current flow conductedbetween the first and second electrode branches 111 and 131 uniformoverall, a uniform interval is maintained between the first and secondelectrode branches 111 and 131.

The insulating part 140 may be formed on the upper surfaces of theconductive semiconductor layers 110 and 130. In this case, preferably,the height (or thickness) of the insulating part 140 may be lower (orsmaller) than that of the first and second electrode branches 111 and131 or may be equal to that of the first and second electrode branches111 and 131 in the meaning that it is within the margin of error (ortolerance) in the process. With such a configuration, at least a portionof the upper surface of each of the first and second electrode branches111 and 131 can be exposed and can be easily electrically connected toeach of the first and second electrode pads 112 and 132.

The first and second electrode pads 112 and 132 are formed on the firstand second electrode branches 111 and 131, and are electricallyconnected with the first and second electrode branches 111 and 131,respectively. In the present exemplary embodiment, the first and secondelectrode pads 112 and 132 are provided such that they are in directcontact with the exposed upper surfaces of the first and secondelectrode branches 111 and 131. Also, the first and second electrodepads 112 and 132 are physically separated from the first and secondconductive semiconductor layers 110 and 130 by means of the insulatingpart 140 and electrically connected to the first and second conductivesemiconductor layers 110 and 130 only through the first and secondelectrode branches 111 and 131.

Accordingly, current can be uniformly distributed regardless of theshape and width of the first and second electrode pads 112 and 132 andthe interval between the first and second electrode pads 112 and 132. Indetail, in the related art semiconductor light emitting device, theelectrode pads, as well as the electrode branches, are also formed to bein direct contact with the semiconductor layer. In this case, althoughthe interval between the electrode branches is uniformly maintained, theinterval between the pads which have a relatively large width and areaand the interval between the pads and the electrode branches aredifferent from the interval between the electrode branches which areuniformly maintained, making the current flow through the semiconductorlayer non-uniform overall. Comparatively, in the present exemplaryembodiment, only the first and second electrode branches 111 and 131 arein direct contact with the semiconductor layers, while the first andsecond electrode pads 112 and 132 are spatially separated from the firstand second conductive semiconductor layers 110 and 130 and electricallyconnected to the first and second conductive semiconductor layers onlythrough the first and second electrode branches 111 and 131. Thus,compared with the related art structure, the current flow can besignificantly improved by simply maintaining the uniform intervalbetween the first and second electrode branches 111 and 131.

Preferably, the first and second electrode pads 112 and 132 arepositioned to be as distant as possible from each other. For example, asshown in FIG. 1 a, the first and second electrode pads 112 and 132 areformed at the respective opposed corners on the upper surface of theinsulating part 140, thereby improving the current flow distribution.

FIGS. 2 a and 2 b are a schematic sectional view and a plan view of asemiconductor light emitting device according to an exemplary embodimentof the present invention. Specifically, FIG. 2 a is a sectional viewtaken along line Y-Y′ of FIG. 2 b.

With reference to FIGS. 2 a and 2 b, the semiconductor light emittingdevice according to the present exemplary embodiment has the sameconfiguration as that of the semiconductor light emitting deviceaccording to the former exemplary embodiment described above withreference to FIGS. 1 a and 1 b, except that first and second conductivevias 213 and 233 are formed between first and second electrode pads 212and 232 and first and second electrode branches 211 and 231 and aninsulating part 240 covers the entire upper surfaces of the first andsecond conductive semiconductor layers 210 and 230 including the uppersurfaces of the first and second electrode branches 211 and 231.Hereinafter, the configuration of the first and second conductive vias213 and 233 and their connective relationships will now be described indetail.

In the present exemplary embodiment, the insulating part 240 insulatesthe first and second electrode branches 211 and 231 by covering them,and the at least one first conductive via 213 is formed at an area ofthe insulating part 240 such that it is electrically connected to thefirst electrode branch 211 through the insulating part 240 (i.e., in apenetrative manner) in a thicknesswise direction thereof, and the atleast one second conductive via 233 is formed at an area of theinsulating part 240 such that it is electrically connected to the secondelectrode branch 231 through the insulating part 240 (i.e., in apenetrative manner) in the thicknesswise direction thereof. Accordingly,the first and second electrode branches 211 and 231 are completelycovered by the insulating part 240 so as to be insulated and can beconnected to the first and second electrode pads 212 and 232,respectively, through the first and second conductive vias 213 and 233.This configuration of forming the first and second conductive vias 213and 233 is particularly meaningful when the plurality of first andsecond electrode branches 211 and 231 are formed, details of which willbe described later. However, the present invention is not necessarilylimited thereto.

FIG. 3 is a schematic sectional view of a semiconductor light emittingdevice according to another exemplary embodiment of the presentinvention.

With reference to FIG. 3, the semiconductor light emitting deviceaccording to the present exemplary embodiment has the same configurationas that of the semiconductor light emitting device according to theformer exemplary embodiment described above with reference to FIGS. 1 aand 1 b, except that a second electrode 331 includes a transparentelectrode layer 350 formed between the second electrode 331 and a secondconductive semiconductor layer 330, rather than being in direct contactwith the second conductive semiconductor layer 330.

The transparent electrode layer 350 may be made of various materialshaving light transmittance (or transparency), e.g., a material includingITO (Indium Tin Oxide). The transparent electrode layer 350 may also bemade of various other materials having high light transmittance andexcellent electric conductivity and facilitating current spreading tothe entire surface of the second conductive semiconductor layer 330.

FIGS. 4 a to 4 e are a schematic perspective view, a plan view, and asectional view showing a semiconductor light emitting device accordingto another exemplary embodiment of the present invention. Specifically,FIGS. 4 c, 4 d, and 4 e are sectional views taken along lines A-A′,B-B′, and C-C′ in FIG. 4 b.

With reference to FIGS. 4 a to 4 e, the semiconductor light emittingdevice according to present exemplary embodiment includes a firstconductive semiconductor layer 410 including first and second areasalternately disposed and having a stripe shape, an active layer 420disposed on the second area, a second conductive semiconductor layer 430disposed on the active layer 420, first and second electrode branches411 and 431, a first electrode pad electrically connected to the firstelectrode branch 411 and disposed to be separated from the firstconductive semiconductor layer 410, a second electrode pad 432electrically connected to the second electrode branch 431 and disposedto be separated from the second conductive semiconductor layer 430, andan insulating part 440 formed on the first and second conductivesemiconductor layers 410 and 430. At least one first conductive via 413electrically connected to the first electrode branch 411 and at leastone second conductive via 433 electrically connected to the secondelectrode branch 431 may be penetratingly formed through portions of theinsulating part 440 in a thicknesswise direction.

The first and second electrode branches 411 and 431 are formed to beparallel to each other, have a linear shape, and are alternatelydisposed. A first connection part 414 extends from the first electrodepad 412 to the first conductive via 413 along the upper surface of theinsulating part 440 and a second connection part 434 extends from thesecond electrode pad 432 to the second conductive via 433 along theupper surface of the insulating part 440.

Namely, in the present exemplary embodiment, the plurality of first andsecond electrode branches 411 and 431 are alternately disposed.Hereinafter, the respective elements and their connective relationshipswithin the semiconductor light emitting device according to the presentexemplary embodiment will now be described in detail with reference tothe accompanying drawings.

In the present exemplary embodiment, the first and second conductivesemiconductor layers formed on the first and second area, respectively,may have a protrusion and depression structure having a stripe shape inwhich protrusions and depresses are alternately repeated.

As discussed above, the first and second electrode branches 411 and 431are electrically connected to the first and second conductivesemiconductor layers 410 and 430, and may be alternately disposed tohave a stripe shape. With this structure, the interval between the firstand second electrode branches 411 and 431 can be uniform, and accordingto an embodiment, a larger number of first and second electrode branches411 and 431 may be disposed so that the interval between the first andsecond electrode branches 411 and 431 becomes narrower. Accordingly,when current is applied through the electrode branches, a current flowin the interior of the first and second conductive semiconductor layers410 and 430 electrically connected to the electrode branches canuniformly spread in the area between the first and second electrodebranches 411 and 431, rather than being concentrated in one area.

A plurality of first conductive vias 413 may be formed at an area of theinsulating part 440 such that they are electrically connected to thefirst electrode branches 411 through the insulating part 440 (i.e., in apenetrative manner) in a thicknesswise direction, and a plurality of onesecond conductive via 433 may be formed at an area of the insulatingpart 440 such that they are electrically connected to the secondelectrode branches 431 through the insulating part 440 (i.e., in apenetrative manner) in a thicknesswise direction. In this case, theupper surface of the insulating part 440 has a rectangular shape, andthe first and second conductive vias 413 and 433 may be disposed to beadjacent to one side and the other side opposed to the one side,respectively, when viewed from above. Namely, as shown in FIG. 4 b, thefirst and second conductive vias 413 and 433 may be formed in alengthwise direction along the respective sides. Accordingly, the firstand second conductive vias 413 and 433 can be separated as far aspossible from each other and accordingly, the current spreading effectcan be improved.

Also, the first and second conductive vias 413 and 433 can beelectrically connected to the first connection part 414 extending fromthe first electrode pad 412 to the first conductive via 413 along theupper surface of the insulating part 440 and a second connection part434 extending from the second electrode pad 432 to the second conductivevia 433 along the upper surface of the insulating part 440,respectively. In this case, as described above, when the plurality offirst and second conductive vias 413 and 1433 are formed in thelengthwise direction along the respective sides, the first and secondconnection parts 414 and 434 extend along the formation direction so asto be electrically connected to the first and second conductive vias 413and 433. Because the first and second electrode pads 412 and 432 and thefirst and second conductive vias 413 and 433 are connected by the firstand second connection parts 414 and 434, new elements, the first andsecond pads 412 and 432 can be electrically connected through the firstand second through the first and second connection parts 414 and 434,without having to be provided to every first and second electrodebranches 411 and 431. In particular, as mentioned above with referenceto the configuration illustrated in FIGS. 1 to 3, the first and secondpads 412 and 432 may not be limitedly disposed on the first and secondbranch electrodes 411 and 431; namely, the first and second pads 412 and432 may be variably selectively disposed on any area of the uppersurface of the insulating part 440 according to embodiments.

One first electrode pad and one second electrode pad may be formed or aplurality of first and second electrode pads may be formed according toembodiments. In the present invention, one first electrode pad 412 andtwo second electrode pads 432 are illustrated to be disposed. In thiscase, the first and second electrode pads 412 and 432 are formed to beadjacent to the sides opposed on the upper surface of the insulatingpart 440 having a rectangular shape and, in particular, the firstelectrode pad 412 is positioned at an area spaced apart by the samedistance from the two second electrode pads 432, the current can spreadmore effectively.

As set forth above, according to exemplary embodiments of the invention,light extraction efficiency can be improved by implementing excellentcurrent spreading.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

What is claimed is:
 1. A semiconductor light emitting device comprising:a first conductive semiconductor layer including first and second areasin a plan view; an active layer disposed on the second area; a secondconductive semiconductor layer disposed on the active layer; first andsecond electrode branches disposed on the first and second conductivesemiconductor layers, respectively; a first electrode pad electricallyconnected to the first electrode branch and disposed on the firstelectrode branch; a second electrode pad electrically connected to thesecond electrode branch and disposed on the second electrode branch; anda transparent electrode layer disposed on the upper surface of thesecond conductive semiconductor layer; wherein the first and secondelectrode branches have a stripe shape in the plan view and widths ofthe electrode branches at least nearest contact regions between branchesand pads are less than widths of the pads.
 2. The device of claim 1,wherein the first and second electrode branches are laterally disposedand mutually parallel.
 3. The device of claim 1, wherein the secondelectrode branch is disposed on an upper surface of the transparentelectrode layer.
 4. A semiconductor light emitting device comprising: afirst conductive semiconductor layer including first and second areas;an active layer disposed on the second area; a second conductivesemiconductor layer disposed on the active layer; first and secondelectrode branches disposed on the first and second conductivesemiconductor layers, respectively; an insulating part disposed on thefirst and second conductive semiconductor layers, the insulating partallows at least a portion of each of upper surfaces of the first andsecond electrode branches to be exposed; a first electrode pad coveringthe upper surface of the first electrode branch and at least a portionof upper surface of the insulating part; a second electrode pad coveringthe upper surface of the second electrode branch and at least a portionof upper surface of the insulating part; and a transparent electrodelayer disposed on the upper surface of the second conductivesemiconductor layer; wherein the first and second electrode pads areelectrically connected to the first and second electrode branchesrespectively; and widths of the electrode branches at least nearestcontact regions between branches and pads are less than widths of thepads.
 5. The device of claim 4, wherein a plurality of first and secondelectrode branches are alternately disposed.
 6. The device of claim 4,wherein the first and second electrode branches are laterally disposedand mutually parallel.
 7. The device of claim 4, wherein the insulatingpart allows at least a portion of each of upper surfaces of the firstand second electrode branches to be exposed.
 8. The device of claim 7,wherein the insulating part allows at least a portion of each of uppersurfaces of the first and second electrode branches to be exposed. 9.The device of claim 8, wherein the first and second electrode pads aredisposed on the exposed portions of the upper surfaces of the first andsecond electrode branches, respectively.
 10. The device of claim 4,wherein the second electrode branch is disposed on an upper surface ofthe transparent electrode layer.